Recent advances in flat panel display technology have included the advent of flat panel displays that are constructed using Organic Light Emitting Diodes (OLED). This flat panel display technology has many advantages over flat panel displays based on more popular liquid crystal display technology. Unlike liquid crystal displays that use the orientation of liquid crystal materials to modulate light from a large uniform backlight, OLED displays utilize materials that emit light. A full-color display is typically constructed by depositing three different materials that each emits a different color of light onto a substrate to create a full-color display, although they may also be constructed using a single emissive material and a color filter array. Depositing these separate subpixels in different spatial locations allows the construction of a full-color display when the light from the primary colors are integrated by the human eye to allow the perception of a large gamut of colors from three or more primary colors. During this deposition, equal areas of each of the primary colors are commonly deposited onto the substrate.
Unfortunately, when displays are constructed from the OLED materials available today, the lifetime of the display is often limited by the lifetime of one of the OLED materials, typically blue. Therefore, lifetime is one of the primary differentiating factors for this class of displays today. For this reason, the OLED materials that are commonly selected for application within today's OLED displays are selected primarily because they have very good luminance stability over time and/or high luminance efficiency. Further, the materials that are available today with good luminance stability over time and good luminance efficiency are often not very saturated. Therefore, the selection of materials based upon the luminance stability over time or the luminance efficiency of the materials results in displays with limited color gamut. More disturbingly, the selection of materials based on either luminance stability over time or good luminance efficiency does not guarantee that the materials will result in the combination of materials that produces the longest lifetime displays.
In fact, the lifetime of the final display is determined by a complex interaction of factors such as the luminance stability over time, luminance efficiency, and color coordinates of the OLED material, as well as display attributes such as the color temperature and luminance distribution for the display. For example, it is possible to construct a display from a set of red, green, and blue OLED materials and then, by selecting a blue OLED material with poorer luminance stability over time and/or luminance efficiency but with a purer blue primary, create a display with significantly improved lifetime.
There is a need therefore for an improved method for selecting OLED materials during the design of an OLED display to guarantee the selection of materials that provides a final display design with a truly longer life or an optimized tradeoff in display lifetime with display color gamut.